ACIW vs FIS: Which Is the Better Buy in 2026?

Same yardstick, side by side (as of November 2026). Valuation lined up like this is most meaningful for two names in the same corner of the market, which these are. Figures are approximate; verify before investing.

Reading it: FIS is the cheaper of the two on forward earnings, but cheaper is not the same as better. Pair the valuation with growth (how far the forward P/E sits below the trailing P/E) and risk (beta) before you decide.

The metrics above tell you which is the marginally better business. The bigger risk for most people is not picking the slightly worse stock, it is over-concentrating. ACIW and FIS share themes, so owning both, or adding either to what you already hold, can quietly push a large share of your portfolio into one bet.

This is the part a generic comparison page cannot answer, because it depends on what you own. Connect your brokerage and Walnut shows your real, combined ACIW and FIS exposure, flags overlap with your existing positions, and tells you if adding one would tip you past a concentration you are comfortable with, read-only by default, with your login staying at your broker. Walnut is not an investment adviser.

ACI Worldwide, Inc. builds the software that moves and manages payments behind the scenes. Founded in 1975 and headquartered in Florida, the company sells payment hubs and real-time payment engines to banks and processors, authorization and orchestration software to large merchants, machine-learning fraud detection across both, and, through its Biller segment, electronic billing and digital collections for utilities, insurers, telecoms, healthcare providers and government agencies. After a 2025 reorganization the business reports in two segments: Payment Software (the former banking and merchant units combined) and Biller. Its customers are institutional and sticky, deployments run for years, and a meaningful share of revenue comes from outside the United States.

Full ACIW guide

Fidelity National Information Services, Inc. is a global financial-technology company that provides the software and services banks, capital-markets firms, and merchants run on. It operates mainly through two segments, Banking Solutions (core processing, digital banking, payments, and related software for financial institutions) and Capital Market Solutions (trading, treasury, lending, and risk technology for buy-side and sell-side firms). FIS serves more than 20,000 clients across over 130 countries and processes trillions of dollars in transactions each year, which makes it more of an embedded infrastructure vendor than a consumer-facing brand. Because its software is woven into clients' daily operations, revenue is heavily recurring and switching costs are high.

Full FIS guide

Both fit overlapping themes, but they are not interchangeable. The useful comparison is which set of drivers and risks you want exposure to.

• ACIW drivers: Real-time payments modernization; The shift from license to subscription.
• FIS drivers: Sticky, recurring banking software; Capital Markets momentum.

A faster-growing, richer-valued name usually swings harder, so it suits a longer horizon and a higher tolerance for volatility; a steadier, more cash-generative business suits a more conservative or income-minded investor. The honest test is which set of risks you could hold through a drawdown: The single most persistent issue is revenue lumpiness: term license renewals concentrate in particular quarters, so reported growth and GAAP earnings can swing sharply on the timing of a handful of large bank contracts, and quarterly GAAP net income ranged from ~$32 million to ~$91 million over the past four quarters even as trailing revenue reached ~$1.82 billion. For FIS, the main risk is that FIS is a mature, slower-growing business competing against strong rivals, so growth can disappoint if bank IT spending softens or clients delay projects.

Growth-minded investors who believe the theme has years to run tend to accept the richer multiple for more upside; value-minded investors lean toward the cheaper forward earnings and steadier profile. Pick ACIW if you believe its drivers more; FIS if you believe its. Many investors hold both, but since they share themes, that is a concentrated bet, not diversification. Decide deliberately and check overlap. For the full detail, see the ACIW and FIS guides.

ACIW. At ~$51.99 on October 16, 2026, ACIW trades at roughly 24 times trailing GAAP earnings but only about 13 times forward estimates, because consensus expects 2026 EPS of ~$3.60 and 2027 EPS of ~$3.90 as license renewals land, heavily in the fourth quarter. Trailing free cash flow of ~$261 million against net debt of roughly $700 million is comfortable coverage for a software business. Third-quarter results are due November 5, 2026, with consensus at ~$0.61 EPS on ~$422 million of revenue.

FIS. At ~$35.94 FIS trades near 5.4x forward adjusted earnings and ~11x EV/EBITDA, a deep discount to software peers that reflects slower guided growth, ~$21 billion of debt and doubts about the Issuer Solutions deal. The January 2026 transactions make reported and pro forma growth figures diverge sharply, and the trailing P/E is depressed by the one-time Worldpay gain, so check which basis a number uses. The November 3 report will show whether margin gains and free cash flow keep outrunning the reduced revenue outlook.

Headline figures (approximate, October 2026): ACIW shows market cap ~$5.3B, revenue (ttm) ~$1.82B (Q2 2026 up ~7.3% yoy), net income (ttm) ~$226M (~12% margin), eps (ttm) ~$2.19; FIS shows revenue (ttm) ~$12.2 billion (latest quarter ~+29% reported, mainly Issuer Solutions consolidation), 2026 pro forma revenue growth guidance ~4.5-5% (lowered at Q2 2026); consensus revenue ~$13.7 billion, adjusted ebitda margin ~41.7% pro forma in Q2 2026 (up ~113 bp), adjusted eps (q2 2026) ~$1.48 vs ~$1.47 expected; 2026 consensus ~$6.19.

ACIW and FIS are related but distinct: same themes, different businesses and risks. Neither wins in the abstract; the right pick is whichever thesis you actually believe, sized so you are not over-concentrated in one theme. Walnut can show your combined ACIW and FIS exposure against your real portfolio. It is not an investment adviser.