Is it correct to say Accepting payments was never this simple and easy -- I am concerned about the plural + was; is that correct?
Accepting payments was never this simple and easy.
The subject of the verb was is not payments, but the verbal accepting, which is singular. Commonly called a gerund — the -ing form of a verb functioning as a noun phrase — a verbal such as accepting can still take complements like payments or be modified by adverbs just as any verb:
Conveniently accepting payments is a big part of any successful business... — Merchant Account Solutions
When the -ing form of the verb takes a plural and can be modified by adjectives, then it is no longer a verbal, but a deverbal noun that functions as any other noun:
They reflect the investors' view that the then current earnings were only temporarily low and that they would improve as economic conditions returned to normal. In the usual case, abnormally high earnings are viewed with skepticism… — Alan E. Grunewald, Stock Valuation in Federal Taxation, 1961, 85.
The remarkable thing about gerunds is that if two or more are joined by a coordinating conjunction in the subject of a clause, they still take a singular verb if considered a single action, task, or state:
Despite its plural construction, Feeling gratitude and not expressing it describes a single state, thus takes a singular verb. How a writer wishes to depict an action/state, as single or separate, determines whether the verb is singular or plural:
Washing and ironing a shirt costs US$1.10. — La Ruta Maya, Yucatán, Guatemala & Belize: A Travel Survival Kit, 1991.
Washing and ironing were hard, hot work, done under cramped conditions. — Nancy F. Cott, Domestic Ideology and Domestic Work, Part 2, 1992, 348.
Unless you are exceedingly lucky, starting and running a small business is a very time-consuming and emotionally draining process. — U.S. News & World Report, 91 (1981), 75.
Starting a small business and running it successfully are no easy tasks. — Business Development Bank of Canada.
And no matter how many gerunds or how many objects, if the task itself is seen as one activity, then the verb is still singular:
02.01.2018 · Cleaning and maintaining swimming pools, spas, fountains, artificial waterfalls or koi ponds is hard work and requires following specific rules… — Gold Coast Pool & Spa.