Rendon, 29, is set to become a free agent for the first time in his career following the conclusion of the 2019 World Series.
The deal was originally tendered in early September. With free agency so close, the offer is not expected to prevent Rendon from exploring other options.
The third baseman is coming off the best season of his career, setting highs in home runs, batting average, on-base percentage, and slugging percentage, while leading all of baseball in RBIs.
Rendon, a Scott Boras client, is a little over one month away from becoming the most coveted hitter on the open market.
Free agency will officially open five days after the final game of the World Series, with the Nats likely to tender their All-Star and Silver Slugger a one-year qualifying offer, thereby attaching Rendon to draft-pick compensation in the event he signs elsewhere.
The reported contract offer is said to be structured similarly to Max Scherzer's, with limited deferrals all being paid within seven years of the expiration of the deal.
The Nationals are set to host the Milwaukee Brewers for the NL wild-card game on Tuesday, with the winner going on to face the Los Angeles Dodgers.