Late last year, I wrote that shares of off-price retail giant TJX Companies (NYSE:TJX) could reach $100 in 2018, driven by the benefit from a lower corporate tax rate, as well as continued strong sales growth.

TJX stock is now closing in on that symbolic milestone. The stock hit a new all-time high on Monday, ending the day at $97.56: up 28% year to date. Shares of smaller rival Ross Stores (NASDAQ:ROST) also reached a new all-time high on Monday. However, Ross Stores stock is up a far more modest 9% year to date.

TJX Chart

TJX and Ross Stores Year-to-Date Stock Performance, data by YCharts.

TJX stock now trades for 20 times its projected earnings for the current year. Ross Stores shares are slightly more expensive, at 21 times earnings. Nevertheless, both stocks may have room to run -- particularly TJX.

First-quarter results were very strong

Last quarter, TJX and Ross Stores both posted solid 3% comp sales increases. Store openings are adding to both companies' growth rates, driving an 11.6% revenue increase for TJX and an 8.5% revenue gain for Ross Stores.

Meanwhile, adjusted earnings per share surged 38% year over year at TJX and 35% at Ross Stores. Tax reform drove most of the EPS growth, but each company's earnings increased by double digits on an organic basis, too.

Both companies warned investors that this rate of sales and earnings growth may not continue. TJX noted that rising freight costs and currency fluctuations could cut into its profitability during the rest of the fiscal year, while Ross Stores' management pointed to some expenses that shifted from the first quarter to the second quarter.

Forecasts are probably conservative

Analysts currently expect that TJX and Ross Stores will each produce full-year EPS just a few pennies above the high end of their respective forecast ranges. Given that both companies routinely provide extremely conservative guidance, these EPS estimates are probably too low.

The exterior of a Ross Dress for Less store.

TJX and Ross Stores routinely publish conservative forecasts. Image source: Ross Stores.

For one thing, TJX and Ross Stores both seem to be projecting that comp sales growth will slow from the first quarter's pace, even though both were negatively impacted by unfavorable weather trends last quarter.

Furthermore, retail sales growth has been accelerating in 2018, lifted by low unemployment and individuals' tax savings. Over the past three months, retail sales at clothing stores surged 5.7% year over year. Sales at general merchandise stores rose 3.1%, while furniture and home furnishing stores (which would presumably include TJX's HomeGoods chain) saw 5.7% growth. This is even stronger retail sales growth than the multiyear high achieved in 2017.

Thus, there's a good chance that comp sales growth accelerated this quarter at TJX and Ross Stores, and growth could remain at an elevated level for the next few quarters. After all, both retailers have averaged 4% annual comp sales increases over the past three years.

Competitors' bankruptcies are creating new growth potential

Looking to the second half of 2018, TJX and Ross Stores are set to benefit from two prominent retail bankruptcies. Toys R Us recently finished liquidating the last of its stores, while regional department store chain Bon-Ton Stores will close up shop by the end of August.

These liquidations should create ample buying opportunities for off-price retailers, as vendors scramble to sell merchandise that otherwise would have gone to Toys R Us or Bon-Ton. In addition, the disappearance of these chains could drive further market share gains for TJX and Ross Stores.

TJX is probably in better position to capitalize on these developments. First, it does more of its buying at the last minute than Ross Stores. Second, Ross Stores doesn't have much of a presence in the Northeast, which is where Bon-Ton operated lots of stores. As a result, 74% of Bon-Ton locations have a TJX store within five miles; only 28% have a Ross store within that radius.

Thus, both off-price giants could be poised for further share price gains if they can capitalize on their near-term growth opportunities over the next few quarters. However, TJX still seems to have more upside than Ross Stores.