Donald Trump and the Republican National Committee finalized a joint fundraising agreement late Tuesday that would allow individual donors to write checks of as much as $449,400—far higher than the $2,700 cap on what the presumptive GOP nominee’s presidential campaign can accept.

Under the agreement, Mr. Trump’s campaign and the RNC will raise money for two joint fundraising committees. The first, called Trump Victory, will raise money for the RNC, the campaign and 11 state party committees. The second, called Trump Make...